[pjsip] Service-route overriding proxy

Olivier Beytrison olivier at heliosnet.org
Sun Nov 4 07:55:35 EST 2007

I've been thinking about it yesterday again, and when you take in
consideration the whole concept of the Service-Route header (at least in
an IMS architecture), it makes sense.

During a registration on IMS
1. the UA send the initial register to the P-CSCF
2. the P-CSCF locates the I-CSCF through NAPTR/SRV requests
3. the P-CSCF forwards the REGISTER to the I-CSCF
4. the I-CSCF interrogate the HSS to discover which S-CSCF
   should serve this Private Address
5. the I-CSCF forwards the REGISTER to the S-CSCF
6. the S-CSCF process the request and add the Service-Route in the answer

So the goal of the Service-Route is to avoid all this process to locate
the correct S-CSCF which should serve this request, by having the UA
appending it to the Route header in all request after a Register.

this doesn't change the fact that, from where you're connecting, you
need to go through a small SIP proxy which acts like an
application-level firewall. And this SIP proxy should be an outbound_proxy.

Anyway, thx for the modification

Have a nice sunday


Benny Prijono a écrit :
> Sorry for not coming back to the list with the info. So yeah, for 
> now I use the append approach, so the Service-Route will be appended 
> to both outbound and account proxies. I prefer this one since it is 
> simpler, no need to add new option, and it is somewhat backward 
> compatible with existing config. But if it proves to be the wrong 
> choice I'm willing to consider the alternative (adding 
> --acc-outbound option).
> cheers,
>   -benny
> Olivier Beytrison wrote:
>> Sorry, nevermind my last mail, I should have check the svn before
>> sending it.
>> Thanks a lot Benny
>> Olivier
>> Benny Prijono a écrit :
>>> Okay, thanks for the info.
>>> So is appending Service-Route to existing/preconfigured route set 
>>> the best approach? Any potential pitfalls with this? (I can't think 
>>> of any).
>>>   -benny
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 Olivier Beytrison
 Telecommunication Engineer
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 Mail: olivier at heliosnet.org
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